Thursday, April 13, 2006

What Pianka really thinks

I have two grandchildren and I want them to inherit a stable Earth. But I fear for them. Humans have overpopulated the Earth and in the process have created an ideal nutritional substrate on which bacteria and viruses (microbes) will grow and prosper. We are behaving like bacteria growing on an agar plate, flourishing until natural limits are reached or until another microbe colonizes and takes over, using them as their resource. In addition to our extremely high population density, we are social and mobile, exactly the conditions that favor growth and spread of pathogenic (disease-causing) microbes. I believe it is only a matter of time until microbes once again assert control over our population, since we are unwilling to control it ourselves. This idea has been espoused by ecologists for at least four decades and is nothing new. People just don't want to hear it.

[Translation: we humans are setting up the conditions for nasty diseases]

Population crashes caused by disease have happened many times in the past. In the 1330s bubonic plague killed one third of the people in Europe's crowded cities. Smallpox and measles decimated Native Americans when Europeans transported them to the new world. HIV is a relatively new disease wreaking havoc in Africa and Asia. Another population crash is inevitable, but the next one will probably be world-wide.

[History shows we have suffered from pandemics in the past, and we can inductively conclude we will again]

People think unrealistically because they have lost touch with the natural world. Many people today do not really know where and how our food is produced, and on what our life support systems are based. As we continue paving over natural habitats, many think that we can disrupt and despoil the environment indefinitely. We have already taken half of this planet's land surface. Per capita shares of all the things that really matter (air, food, soil, and water) are continuously falling. Our economic system is based on the principle of a chain letter: growth, growth, and more growth. Such runaway growth only expands a bubble that cannot be sustained in a finite world. We are running out of virtually everything from oil, food and land to clean air and water.

[We are using more resources than we can sustain]

Some politicians, economists, and corporations want us to believe that technology will come to our rescue. But we have a false sense of security if we think that science can respond quickly enough to minimize threats from emerging diseases. Microbes have such short lifecycles that they can evolve exceedingly fast, much faster than we can respond to them. Many bacteria have evolved resistance to most antibiotics, and viruses are resistant to just about anything. Defense always lags behind offense. So far, modern humans have just been lucky. A reactive approach to problems isn't enough, we also need to be proactive and anticipate problems before they become too severe to keep them from getting out of control.Many people believe that Earth and all its resources exist solely for human benefit and consumption, this is anthropocentrism. We should allow the millions of other denizens of this Earth some space to live -- they evolved here just as we did and have a right to this planet, too.

[Technology will not be able to solve the problem because disease evolves faster than technology can]

I do not bear any ill will toward humanity. However, I am convinced that the world WOULD clearly be much better off without so many of us. Simply stopping the destruction of rainforests would help mediate some current planetary ills, including the release of previously unknown pathogens. The ancient Chinese curse "may you live in interesting times" comes to mind -- we are living in one of the most interesting times humans have ever experienced. For example, consider the manifold effects of global warming. We need to make a transition to a sustainable world. If we don't, nature is going to do it for us in ways of her own choosing. By definition, these ways will not be ours and they won't be much fun. Think about that.

[The ecosystem would be more viable if we didn't do what we do, and if we don't stop it, disease will end up culling the human population]

So, let's consider each of these claims, as I have summarized them:

1. we humans are setting up the conditions for nasty diseases2. History shows we have suffered from pandemics in the past, and we can inductively conclude we will again

This is clearly true. Disease reservoirs exist among human populations and animal populations around the world. Local populations will have adapted to them, either through immunological or genetic pathways, but once they reach "naive" populations, they will be able to spread rapidly.

Paul Ewald, in his marvellously clear book "Evolution of Infectious Disease", argued that the virulence of a pathogen ("virulence" means something like, exploits the host without concern for the host's viability) is determined by the nature of selection in a population. Not the population of the hosts as such, but of the pathogens themselves. Here's why.

Suppose a disease is passed on at a rate roughly equivalent to the reproductive rate of the host (say, you infect a score or less, or it is passed down mostly through your children). Any mutant form of the pathogen will be less fit than a non-mutation, because those hosts infected by the non-mutant won't die before infecting more hosts, while the virulent one will succeed in infecting fewer hosts even though it controls the host's resources that it has infected.

Now suppose that the disease can spread easily, say, through airborne vectors or water. Now, the race is on. The ones that exploit the host and rush on to the next will be fitter than the ones that just sit there quietly doing their thing. So virulence will increase. The reason why AIDS has decreased in virulence in many countries is because the rate of infection was dramatically lowered by the use of condoms. In countries that ignore or oppose the use of condoms, the virulence is higher because the genetic interests of the host and the pathogen do not coincide.

There is no prescription here. Just a statement of the facts. When a pathogen reaches a "naive" population, the more virulent mutants will spread faster than the less virulent ones, because the rate of infection, due to a lack on inherent resistance, is high. Eventually resistance genes (genes that happen to confer some resistance, like the CCR5 allele which blocks some infection by smallpox, bubonic plague, and, as it happens, HIV) will spread, if they exist, and there will be an equilibrium. The Black Death showed this - it killed around one in three. But typically, if the disease uses the same routes to infection as other related diseases, then it is very much less than this. The Spanish Flu epidemic of World War I killed only 2.5%.

3. We are using more resources than we can sustain

I don't see how anyone can deny this. China alone is using coal and oil at a fantastic rate, and the use of wood in South East Asia and South America to feed the paper industry alone is destroying important, nay, vital, ecosystems. What seems to have happened is that we institutionalized the over-use of resources at a rare moment in history, post-War America. And because we did that then, we have falsely inferred that we can always do this. It doesn't help that the economic interests of industries that were founded or made global at that time control most of the policy making in the nations that really count (America, Europe, the "First World"), forcing developing and underdeveloped (even the terms are loaded!) nations to follow suit or lose any self-determination.

4. Technology will not be able to solve the problem because disease evolves faster than technology can

He means "medical technology", but "food production technology" is also at risk. Diseases strike all organisms, including crops. The Botryitis plague of European grapes, the ergot infection of seed grains that sparked the witch craze, and so on show this, but crop diseases are only part of the problem. Moreover, introduced species in ecosystems that are unable to curb their population growth is also going to affect food production, particularly in overcrowded nations.

Note: no prescriptions here either. And nothing new. All this has been known, and stated, many times.

So, what is wrong with Pianka's claims? The "90%" dieoff claim is one I take issue with. There is no evidence that this will happen based on either prior knowledge or immunology, in my view. What is more likely, though, is that reproductive rates will decline as health and food decreases. In short, we might very well be heading for a society of constantly ill people trying to grow food unsuccessfully, hardly the preconditions for a noble life. But as population declines (and the infrastructure that a large population of non-food-producers permits) so will the basis of technological society. If all the linesmen are out growing wheat and cattle, who's going to support my Internet connection? Or maintain telephones? Of deliver post? and so on. The "post-apocalyptic" society so often envisaged in dystopian science fiction may come gradually rather than suddenly. Less dramatic, equally bad, or worse.

Over some suitably long period, yes, the population will inevitably decline to 10%. But it may not happen through pandemics. They will contribute, but they won't be the major cause, I believe.

So, now to the hard question - the one that all the right wing bloviators have jumped on: is this a good thing? Clearly, no. If we could support our society and population indefinitely, while having a working ecosystem that includes fishing, farming and manufacturing, sure it would be good. But, as a matter of fact, we can't. So faced with a hard choice, what is best? That we take steps to solve it ourselves, or face a more or less rapid decline into medievalism, only this time without the hope of getting out of it, because all the materielle we need to do so has already been used...

That isn't social darwinism. It isn't euthanasia or eugenics. It isn't even conservative or radical politics. It's just damned fact. On this, Pianka is right. Somebody should tell the emperor he's wearing too many clothes.